Vises, clamps and other clamping devices normally comprise two parallel jaws that move toward each other to clamp a work piece between them. Typically such jaws have flat clamping surfaces that are suited to clamp a work piece with at least one substantially planar surface that is engaged by the clamping surface. Many times, however, such vises are used in the machining of irregularly shaped or circular pieces merely by tightening the device sufficiently to prevent movement during a machining operation. In many situations, however, this will deform the work piece or, particularly with finished work pieces, mar the surface.
More specifically, such vises often times clamp a work piece on a drill press, milling machine or other similar machine tools for drilling or machining operation. For example, if it is necessary to work on a circular object, that clamping forces are exerted only along opposite disposed tangential lines of the work piece. As a result it is very difficult to maintain the work piece in a stable position, particularly if the working forces are exerted off the line between these two clamping lines, and even if the clamping forces are large.
In such situations it is commonplace to build a special fixture, or jig, that clamps the work piece directly onto a clamping surface. For example, Mead discloses a special hold down clamp on a fixture to be mounted on a drill press or milling machine work table. Of course the manufacture or construction of such jigs for a one-time machining operation can greatly extend machining times and increase overall machining costs.
Paulsen discloses modifications to a conventional vise to include pins that are permanently mounted on the top surface of two jaw structures. These pins are stated to be useful in holding annular articles. However, the pins are fixed in the jaws and are displaced from the clamping surfaces. They do not provide great flexibility for accommodating irregularly shaped objects of a wide range of sizes and shapes. Moreover, the vise itself must be modified which is not an easy task after manufacture.
Hickman discloses a workbench with beams that form elongated vise jaws. These beams include a number of holes. Special pins can be located in an arbitrary array in the holes to clamp irregular objects between or among the pins. While this array of holes on the vise beams provides flexibility, it also increases the size of the vise jaws and requires special machining of the vise jaws, such as disclosed by Paulsen.
Hennessey discloses a work piece positioning block with a plurality of horizontal holes extending in from a clamping face on the block. Dowels or pins selectively inserted in the holes orient a work piece in a vertical plane when a supporting vise is closed, thereby clamping the work piece between one of the vise jaws and the work piece positioning block.
Eibert discloses a special fixture for straightening type letters. A unitary bracket positioned between vise jaws contains insets that contact opposite sides of a type lever at spaced locations along its length. One of the insets is movable when one of the clamp jaws engages a bolt to displace it and force that inset on one side toward the opposite stationary insets thereby to deform the type lever.
Daley discloses a support for cylindrical work pieces that includes two hinged plates. One plate is fixed to a drill press table or other work table. The second hinged plate has holes for receiving dowel pins that are arranged to support the work piece when the second plate is raised to some angle or to allow a separate clamp to affix a work piece to the second plate when it is vertical.
Each of the foregoing patents discloses a jig or fixture that are used with jaws for supporting circular or irregularly shaped work pieces. However, Paulsen and Hickman require a direct modification to the clamping device; Hennessey and Daley provide a direct clamping of the work piece by at least one of the jaws. Mead discloses a specific hold down arrangement. There is no disclosure of a simple fixture that can be used to support an irregularly shaped or circular work piece for subsequent machining or other operations on a machine tool or the like in a conventional vise or like device.